Methods and apparatus for grant processing

ABSTRACT

Certain aspects of the present disclosure relate to methods and apparatus for grant processing in uplink centric subframes. An example method generally includes transmitting a first subframe comprising a first grant that includes information for one or more transmissions on that allocated resources in the first subframe to a user equipment (UE) and transmitting the first subframe, with a second grant that allocates resources in at least a second subframe to occur after the first subframe. Other aspects, embodiments, and features are also claimed and described.

CLAIM OF PRIORITY UNDER 35 U.S.C. § 119

This application claims benefit of U.S. Provisional Patent ApplicationSer. No. 62/288,428, filed Jan. 28, 2016, which is herein incorporatedby reference in its entirety

TECHNICAL FIELD

Certain aspects of the present disclosure generally relate to wirelesscommunications, and more particularly, to grant processing in uplinkcentric subframes. Embodiments enable and provide efficientcommunication protocols (e.g., link grants) for helping ease processingtime (e.g., for downlink and uplink frame/sub-frame processing), improvepower conservation, and positively benefit user experience.

INTRODUCTION

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power). Examples of such multiple-access technologies includecode division multiple access (CDMA) systems, time division multipleaccess (TDMA) systems, frequency division multiple access (FDMA)systems, orthogonal frequency division multiple access (OFDMA) systems,single-carrier frequency divisional multiple access (SC-FDMA) systems,and time division synchronous code division multiple access (TD-SCDMA)systems.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example of an emergingtelecommunication standard is Long Term Evolution (LTE).LTE/LTE-Advanced is a set of enhancements to the Universal MobileTelecommunications System (UMTS) mobile standard promulgated by ThirdGeneration Partnership Project (3GPP). It is designed to better supportmobile broadband Internet access by improving spectral efficiency, lowercosts, improve services, make use of new spectrum, and better integratewith other open standards using OFDMA on the downlink (DL), SC-FDMA onthe uplink (UL), and multiple-input multiple-output (MIMO) antennatechnology. However, as the demand for mobile broadband access continuesto increase, there exists a need for further improvements in LTEtechnology. Preferably, these improvements should be applicable to othermulti-access technologies and the telecommunication standards thatemploy these technologies.

BRIEF SUMMARY OF SOME EMBODIMENTS

The following summarizes some aspects of the present disclosure toprovide a basic understanding of the discussed technology. This summaryis not an extensive overview of all contemplated features of thedisclosure, and is intended neither to identify key or critical elementsof all aspects of the disclosure nor to delineate the scope of any orall aspects of the disclosure. Its sole purpose is to present someconcepts of one or more aspects of the disclosure in summary form as aprelude to the more detailed description that is presented later.

Certain aspects of the present disclosure provide a method for wirelesscommunications by a base station. The method generally includestransmitting a first subframe comprising a first grant that includesinformation for one or more transmissions on allocated resources in thefirst subframe to a user equipment (UE) and transmitting the firstsubframe with a second grant that allocates resources in at least asecond subframe to occur after the first subframe.

Certain aspects of the present disclosure provide an apparatus forwireless communications by a base station. The apparatus generallyincludes at least one processor configured to generate a first grantthat includes information for one or more transmissions on allocatedresources in a first subframe and generate a second grant that allocatesresources in at least a second subframe to occur after the firstsubframe. The apparatus also generally includes a transmitter configuredto transmit the first grant and the second grant in the first subframe.

Certain aspects of the present disclosure provide an apparatus forwireless communications by a base station. The apparatus generallyincludes means for transmitting a first subframe comprising a firstgrant that includes information for one or more transmissions onallocated resources in the first subframe to a user equipment (UE) andmeans for transmitting the first subframe with a second grant thatallocates resources in at least a second subframe to occur after thefirst subframe.

Certain aspects of the present disclosure provide a non-transitorycomputer-readable medium for wireless communications by a base station.The non-transitory computer-readable medium generally includesinstructions for transmitting a first subframe comprising a first grantthat includes information for one or more transmissions on, allocatedresources in the first subframe to a user equipment (UE) andtransmitting a second grant, in the first subframe, that allocatesresources in at least a second subframe to occur after the firstsubframe.

Certain aspects of the present disclosure provide a method for wirelesscommunications by a user equipment. The method generally includesreceiving, in a first subframe, a first grant that includes informationfor one or more transmissions on allocated resources in the firstsubframe to the UE and receiving, in the first subframe, a second grantthat allocates resources in at least a second subframe to occur afterthe first subframe.

Certain aspects of the present disclosure provide an apparatus forwireless communications by a user equipment. The apparatus generallyincludes a receiver configure to receive, in a first subframe, a firstgrant that includes information for one or more transmissions onallocated resources in the first subframe and receive, in the firstsubframe a second grant that allocates resources in at least a secondsubframe to occur after the first subframe.

Certain aspects of the present disclosure provide an apparatus forwireless communications by a user equipment. The apparatus generallyincludes means for receiving, in a first subframe, a first grant thatincludes information for one or more transmissions on allocatedresources in the first subframe to the UE and means for receiving, inthe first subframe, a second grant that allocates resources in at leasta second subframe to occur after the first subframe.

Certain aspects of the present disclosure provide a non-transitorycomputer-readable medium for wireless communications by a userequipment. The non-transitory computer-readable medium generallyincludes instructions for receiving, in a first subframe, a first grantthat includes information for one or more transmissions on allocatedresources in the first subframe to the UE and receiving, in the firstsubframe, a second grant that allocates resources in at least a secondsubframe to occur after the first subframe.

Aspects generally include methods, apparatus, systems, computer programproducts, computer-readable medium, and processing systems, assubstantially described herein with reference to and as illustrated bythe accompanying drawings. “LTE” refers generally to LTE, LTE-Advanced(LTE-A), LTE in an unlicensed spectrum (LTE-whitespace), etc.

Other aspects, features, and embodiments of the present invention willbecome apparent to those of ordinary skill in the art, upon reviewingthe following description of specific, exemplary embodiments of thepresent invention in conjunction with the accompanying figures. Whilefeatures of the present invention may be discussed relative to certainembodiments and figures below, all embodiments of the present inventioncan include one or more of the advantageous features discussed herein.In other words, while one or more embodiments may be discussed as havingcertain advantageous features, one or more of such features may also beused in accordance with the various embodiments of the inventiondiscussed herein. In similar fashion, while exemplary embodiments may bediscussed below as device, system, or method embodiments it should beunderstood that such exemplary embodiments can be implemented in variousdevices, systems, and methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a network architecture,according to certain aspects of the present disclosure.

FIG. 2 is a diagram illustrating an example of an access network,according to certain aspects of the present disclosure.

FIG. 3 is a diagram illustrating an example of a DL frame structure inLTE, according to certain aspects of the present disclosure.

FIG. 4 is a diagram illustrating an example of an UL frame structure inLTE, according to certain aspects of the present disclosure.

FIG. 5 is a diagram illustrating an example of a radio protocolarchitecture for the user and control plane, according to certainaspects of the present disclosure.

FIG. 6 is a diagram illustrating an example of an evolved Node B anduser equipment in an access network, in accordance with certain aspectsof the disclosure, according to certain aspects of the presentdisclosure.

FIGS. 7A and 7B illustrate downlink centric and uplink centricsubframes, according to certain aspects of the present disclosure.

FIG. 8A-8C illustrate existing dynamically-switchable subframestructures for dynamic time division duplexing (TDD), according tocertain aspects of the present disclosure.

FIGS. 9A-9C illustrate some possible solutions to help alleviate theissue of timing associated with same-subframe UL grants in an UL centricsubframe, according to certain aspects of the present disclosure.

FIG. 10 illustrates example operations for a base station, according tocertain aspects of the present disclosure.

FIG. 11 illustrates example operations for a user equipment, accordingto certain aspects of the present disclosure.

FIG. 12 illustrates an example of a cross-subframe split grant approachfor UL grants, according to certain aspects of the present disclosure.

FIG. 13A-13B illustrate different channels in which UL grants may becarried, according to certain aspects of the present disclosure.

FIG. 14. illustrates that an UL grant may be applied to the subframe inwhich it is received, according to certain aspects of the presentdisclosure.

FIG. 15 illustrates transmitting an UL grant within a data portion of aDL centric subframe, according to certain aspects of the presentdisclosure.

DETAILED DESCRIPTION

Aspects of the present disclosure provide techniques and apparatus foralleviating timeline issues associated with grant processing in uplink(UL) centric subframes (i.e., a subframe having more uplink symbols thandownlink symbols. For example, aspects of the present disclosure proposetechniques for alleviating timeline issues associated with grantprocessing in uplink by transmitting multiple grants (e.g. two grants).A first grant that applies to a current subframe (i.e., the subframe inwhich it is received) and a second grant that applies to futuresubframes. Also, in addition certain embodiments enable and providesplitting UL grants into multiple components or portions. This caninclude an initial or first part configured to convey information suchas rank, DMRS, and is sent N subframes before the actual ULtransmission. Part A grant is needed for UE to generate DMRS and thecorresponding PUSCH occurs at least one subframe later. From a firstpart, a UE knows exactly which subframes it is to transmit. And this caninclude a subsequent or second part configured to convey more dynamicresource allocation. A second part can provides modulation and codinginformation info for a channel (e.g., PUSCH) in a present subframe.

Various aspects of the disclosure are described more fully hereinafterwith reference to the accompanying drawings. This disclosure may,however, be embodied in many different forms and should not be construedas limited to any specific structure or function presented throughoutthis disclosure. Rather, these aspects are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art. Based on theteachings herein one skilled in the art should appreciate that the scopeof the disclosure is intended to cover any aspect of the disclosuredisclosed herein, whether implemented independently of or combined withany other aspect of the disclosure. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition toor other than the various aspects of the disclosure set forth herein. Itshould be understood that any aspect of the disclosure disclosed hereinmay be embodied by one or more elements of a claim.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any aspect described herein as “exemplary”is not necessarily to be construed as preferred or advantageous overother aspects.

Although particular aspects are described herein, many variations andpermutations of these aspects fall within the scope of the disclosure.Although some benefits and advantages of the preferred aspects arementioned, the scope of the disclosure is not intended to be limited toparticular benefits, uses, or objectives. Rather, aspects of thedisclosure are intended to be broadly applicable to different wirelesstechnologies, system configurations, networks, and transmissionprotocols, some of which are illustrated by way of example in thefigures and in the following description of the preferred aspects. Thedetailed description and drawings are merely illustrative of thedisclosure rather than limiting, the scope of the disclosure beingdefined by the appended claims and equivalents thereof.

The techniques described herein may be used for various wirelesscommunication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA andother networks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology such asuniversal terrestrial radio access (UTRA), cdma2000, etc. UTRA includeswideband CDMA (WCDMA), time division synchronous CDMA (TD-SCDMA), andother variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856standards. A TDMA network may implement a radio technology such asglobal system for mobile communications (GSM). An OFDMA network mayimplement a radio technology such as evolved UTRA (E-UTRA), ultra mobilebroadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20,Flash-OFDM®, etc. UTRA and E-UTRA are part of universal mobiletelecommunication system (UMTS). 3GPP Long Term Evolution (LTE) andLTE-Advanced (LTE-A), in both frequency division duplex (FDD) and timedivision duplex (TDD), are new releases of UMTS that use E-UTRA, whichemploys OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA,UMTS, LTE, LTE-A and GSM are described in documents from an organizationnamed “3rd Generation Partnership Project” (3GPP). cdma2000 and UMB aredescribed in documents from an organization named “3rd GenerationPartnership Project 2” (3GPP2). The techniques described herein may beused for the wireless networks and radio technologies mentioned above aswell as other wireless networks and radio technologies.

Example Wireless Communications System

FIG. 1 is a diagram illustrating an LTE network architecture 100 inwhich aspects of the present disclosure may be practiced. It should benoted that LTE is only provided for reference and that aspects of thepresent disclosure are not limited to LTE. For example, aspects of thepresent disclosure may also be practiced in other networks usingtechnology such as LTE-Advanced, New Radio (NR), etc.

For example, a BS/evolved Node B (e.g., 106, 108, etc.) and/or UE 102may determine, based on one or more conditions, a maximum modulationorder that is supported for the transmission of control channel(s) bythe eNodeB 106, 108 etc., to the UE(s) 102. As described in more detailbelow, the one or more conditions may be based on control informationthat is transmitted within the control channel(s). Referring to someexamples, the eNB and/or UE may make the determination based on theparticular format of the control information (e.g., which DCI format isused), a coding rate for the control information, one or moreaggregation level(s) used for the control information, which searchspace (e.g., common search space, UE-specific search space, etc.) thecontrol information is transmitted in, the type of identifier that isused to scramble the control information, etc.

The LTE network architecture 100 may be referred to as an Evolved PacketSystem (EPS) 100. The EPS 100 may include one or more user equipment(UE) 102, an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN)104, an Evolved Packet Core (EPC) 110, a Home Subscriber Server (HSS)120, and an Operator's IP Services 122. The EPS can interconnect withother access networks, but for simplicity those entities/interfaces arenot shown. Exemplary other access networks may include an IP MultimediaSubsystem (IMS) PDN, Internet PDN, Administrative PDN (e.g.,Provisioning PDN), carrier-specific PDN, operator-specific PDN, and/orGPS PDN. As shown, the EPS provides packet-switched services, however,as those skilled in the art will readily appreciate, the variousconcepts presented throughout this disclosure may be extended tonetworks providing circuit-switched services.

The E-UTRAN includes the evolved Node B (eNB) 106 and other eNBs 108.The eNB 106 provides user and control plane protocol terminations towardthe UE 102. The eNB 106 may be connected to the other eNBs 108 via an X2interface (e.g., backhaul). The eNB 106 may also be referred to as abase station, a base transceiver station, a radio base station, a radiotransceiver, a transceiver function, a basic service set (BSS), anextended service set (ESS), an access point, or some other suitableterminology. The eNB 106 may provide an access point to the EPC 110 fora UE 102. Examples of UEs 102 include a cellular phone, a smart phone, asession initiation protocol (SIP) phone, a laptop, a personal digitalassistant (PDA), a satellite radio, a global positioning system, amultimedia device, a video device, a digital audio player (e.g., MP3player), a camera, a game console, a tablet, a netbook, a smart book, anultrabook, a drone, a robot, a sensor, a monitor, a meter, or any othersimilar functioning device. The UE 102 may also be referred to by thoseskilled in the art as a mobile station, a subscriber station, a mobileunit, a subscriber unit, a wireless unit, a remote unit, a mobiledevice, a wireless device, a wireless communications device, a remotedevice, a mobile subscriber station, an access terminal, a mobileterminal, a wireless terminal, a remote terminal, a handset, a useragent, a mobile client, a client, or some other suitable terminology.

The eNB 106 is connected by an S1 interface to the EPC 110. The EPC 110includes a Mobility Management Entity (MME) 112, other MMEs 114, aServing Gateway 116, and a Packet Data Network (PDN) Gateway 118. TheMME 112 is the control node that processes the signaling between the UE102 and the EPC 110. Generally, the MME 112 provides bearer andconnection management. All user IP packets are transferred through theServing Gateway 116, which itself is connected to the PDN Gateway 118.The PDN Gateway 118 provides UE IP address allocation as well as otherfunctions. The PDN Gateway 118 is connected to the Operator's IPServices 122. The Operator's IP Services 122 may include, for example,the Internet, the Intranet, an IP Multimedia Subsystem (IMS), and a PS(packet-switched) Streaming Service (PSS). In this manner, the UE 102may be coupled to the PDN through the LTE network.

FIG. 2 is a diagram illustrating an example of an access network 200 inan LTE network architecture in which aspects of the present disclosuremay be practiced. As noted above, LTE is only provided for reference andaspects of the present disclosure are not limited to LTE.

In this example, the access network 200 is divided into a number ofcellular regions (cells) 202. One or more lower power class eNBs 208 mayhave cellular regions 210 that overlap with one or more of the cells202. A lower power class eNB 208 may be referred to as a remote radiohead (RRH). The lower power class eNB 208 may be a femto cell (e.g.,home eNB (HeNB)), pico cell, or micro cell. The macro eNBs 204 are eachassigned to a respective cell 202 and are configured to provide anaccess point to the EPC 110 for all the UEs 206 in the cells 202. Thereis no centralized controller in this example of an access network 200,but a centralized controller may be used in alternative configurations.The eNBs 204 are responsible for all radio related functions includingradio bearer control, admission control, mobility control, scheduling,security, and connectivity to the serving gateway 116. The network 200may also include one or more relays (not shown). According to oneapplication, a UE may serve as a relay.

The modulation and multiple access scheme employed by the access network200 may vary depending on the particular telecommunications standardbeing deployed. In LTE applications, OFDM is used on the DL and SC-FDMAis used on the UL to support both frequency division duplexing (FDD) andtime division duplexing (TDD). As those skilled in the art will readilyappreciate from the detailed description to follow, the various conceptspresented herein are well suited for LTE applications. However, theseconcepts may be readily extended to other telecommunication standardsemploying other modulation and multiple access techniques. By way ofexample, these concepts may be extended to Evolution-Data Optimized(EV-DO) or Ultra Mobile Broadband (UMB). EV-DO and UMB are air interfacestandards promulgated by the 3rd Generation Partnership Project 2(3GPP2) as part of the CDMA2000 family of standards and employs CDMA toprovide broadband Internet access to mobile stations. These concepts mayalso be extended to Universal Terrestrial Radio Access (UTRA) employingWideband-CDMA (W-CDMA) and other variants of CDMA, such as TD-SCDMA;Global System for Mobile Communications (GSM) employing TDMA; andEvolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, and Flash-OFDM employingOFDMA. UTRA, E-UTRA, UMTS, LTE and GSM are described in documents fromthe 3GPP organization. CDMA2000 and UMB are described in documents fromthe 3GPP2 organization. The actual wireless communication standard andthe multiple access technology employed will depend on the specificapplication and the overall design constraints imposed on the system.

The eNBs 204 may have multiple antennas supporting MIMO technology. Theuse of MIMO technology enables the eNBs 204 to exploit the spatialdomain to support spatial multiplexing, beamforming, and transmitdiversity. Spatial multiplexing may be used to transmit differentstreams of data simultaneously on the same frequency. The data streamsmay be transmitted to a single UE 206 to increase the data rate or tomultiple UEs 206 to increase the overall system capacity. This isachieved by spatially precoding each data stream (e.g., applying ascaling of an amplitude and a phase) and then transmitting eachspatially precoded stream through multiple transmit antennas on the DL.The spatially precoded data streams arrive at the UE(s) 206 withdifferent spatial signatures, which enables each of the UE(s) 206 torecover the one or more data streams destined for that UE 206. On theUL, each UE 206 transmits a spatially precoded data stream, whichenables the eNB 204 to identify the source of each spatially precodeddata stream.

Spatial multiplexing is generally used when channel conditions are good.When channel conditions are less favorable, beamforming may be used tofocus the transmission energy in one or more directions. This may beachieved by spatially precoding the data for transmission throughmultiple antennas. To achieve good coverage at the edges of the cell, asingle stream beamforming transmission may be used in combination withtransmit diversity.

In the detailed description that follows, various aspects of an accessnetwork will be described with reference to a MIMO system supportingOFDM on the DL. OFDM is a spread-spectrum technique that modulates dataover a number of subcarriers within an OFDM symbol. The subcarriers arespaced apart at precise frequencies. The spacing provides“orthogonality” that enables a receiver to recover the data from thesubcarriers. In the time domain, a guard interval (e.g., cyclic prefix)may be added to each OFDM symbol to combat inter-OFDM-symbolinterference. The UL may use SC-FDMA in the form of a DFT-spread OFDMsignal to compensate for high peak-to-average power ratio (PAPR).

FIG. 3 is a diagram 300 illustrating an example of a DL frame structurein LTE. A frame (10 ms) may be divided into 10 equally sized sub-frameswith indices of 0 through 9. Each sub-frame may include two consecutivetime slots. A resource grid may be used to represent two time slots,each time slot including a resource block. The resource grid is dividedinto multiple resource elements. In LTE, a resource block contains 12consecutive subcarriers in the frequency domain and, for a normal cyclicprefix in each OFDM symbol, 7 consecutive OFDM symbols in the timedomain, or 84 resource elements. For an extended cyclic prefix, aresource block contains 6 consecutive OFDM symbols in the time domainand has 72 resource elements. Some of the resource elements, asindicated as R 302, R 304, include DL reference signals (DL-RS). TheDL-RS include Cell-specific RS (CRS) (also sometimes called common RS)302 and UE-specific RS (UE-RS) 304. UE-RS 304 are transmitted only onthe resource blocks upon which the corresponding physical DL sharedchannel (PDSCH) is mapped. The number of bits carried by each resourceelement depends on the modulation scheme. Thus, the more resource blocksthat a UE receives and the higher the modulation scheme, the higher thedata rate for the UE.

In LTE, an eNB may send a primary synchronization signal (PSS) and asecondary synchronization signal (SSS) for each cell in the eNB. Theprimary and secondary synchronization signals may be sent in symbolperiods 6 and 5, respectively, in each of subframes 0 and 5 of eachradio frame with the normal cyclic prefix (CP). The synchronizationsignals may be used by UEs for cell detection and acquisition. The eNBmay send a Physical Broadcast Channel (PBCH) in symbol periods 0 to 3 inslot 1 of subframe 0. The PBCH may carry certain system information.

The eNB may send a Physical Control Format Indicator Channel (PCFICH) inthe first symbol period of each subframe. The PCFICH may convey thenumber of symbol periods (M) used for control channels, where M may beequal to 1, 2 or 3 and may change from subframe to subframe. M may alsobe equal to 4 for a small system bandwidth, e.g., with less than 10resource blocks. The eNB may send a Physical HARQ Indicator Channel(PHICH) and a Physical Downlink Control Channel (PDCCH) in the first Msymbol periods of each subframe. The PHICH may carry information tosupport hybrid automatic repeat request (HARQ). The PDCCH may carryinformation on resource allocation for UEs and control information fordownlink channels. For example, the PDCCH may include downlink controlinformation (DCI), which carries control information for both downlinkand uplink transmissions, such as for example, downlink schedulingassignments, uplink scheduling grants, power control commands,information for decoding/demodulating symbols in the downlink,information for encoding/modulating symbols in the uplink, etc.

The eNB may send a Physical Downlink Shared Channel (PDSCH) in theremaining symbol periods of each subframe. The PDSCH may carry data forUEs scheduled for data transmission on the downlink.

The eNB may send the PSS, SSS, and PBCH in the center 1.08 MHz of thesystem bandwidth used by the eNB. The eNB may send the PCFICH and PHICHacross the entire system bandwidth in each symbol period in which thesechannels are sent. The eNB may send the PDCCH to groups of UEs incertain portions of the system bandwidth. The eNB may send the PDSCH tospecific UEs in specific portions of the system bandwidth. The eNB maysend the PSS, SSS, PBCH, PCFICH, and PHICH in a broadcast manner to allUEs, may send the PDCCH in a unicast manner to specific UEs, and mayalso send the PDSCH in a unicast manner to specific UEs.

A number of resource elements may be available in each symbol period.Each resource element (RE) may cover one subcarrier in one symbol periodand may be used to send one modulation symbol, which may be a real orcomplex value. Resource elements not used for a reference signal in eachsymbol period may be arranged into resource element groups (REGs). EachREG may include four resource elements in one symbol period. REGs mayfurther be arranged into control channel elements (CCEs). Each CCE mayinclude nine REGs. Thus, one CCE equals 36 REs. The REGs may bedistributed across one or more symbols periods (e.g., first one, two,three, etc., symbol periods) and/or the system bandwidth throughinterleaving.

The PCFICH may occupy four REGs, which may be spaced approximatelyequally across frequency, in symbol period 0. The PHICH may occupy threeREGs, which may be spread across frequency, in one or more configurablesymbol periods. For example, the three REGs for the PHICH may all belongin symbol period 0 or may be spread in symbol periods 0, 1, and 2.

The PDCCH may occupy one or more CCEs. The number of CCEs in a PDCCHgenerally refers to the PDCCH's aggregation level. The PDCCH may useaggregation level 1, 2, 4, 8, 16, 32, etc. (corresponding to 9, 18, 36,72, 144, 288 REGs, etc., which may be selected from the available REGs,in the first M symbol periods, for example). Only certain combinationsof REGs may be allowed for the PDCCH. In aspects of the present methodsand apparatus, a subframe may include more than one PDCCH.

A UE may know the specific REGs used for the PHICH and the PCFICH.

The UE may search different combinations of REGs for the PDCCH. Thenumber of combinations to search is typically less than the number ofallowed combinations for the PDCCH. An eNB may send the PDCCH to the UEin any of the combinations that the UE will search.

FIG. 4 is a diagram 400 illustrating an example of an UL frame structurein LTE. The available resource blocks for the UL may be partitioned intoa data section and a control section. The control section may be formedat the two edges of the system bandwidth and may have a configurablesize. The resource blocks in the control section may be assigned to UEsfor transmission of control information. The data section may includeall resource blocks not included in the control section. The UL framestructure results in the data section including contiguous subcarriers,which may allow a single UE to be assigned all of the contiguoussubcarriers in the data section.

A UE may be assigned resource blocks 410 a, 410 b in the control sectionto transmit control information to an eNB. The UE may also be assignedresource blocks 420 a, 420 b in the data section to transmit data to theeNB. The UE may transmit control information in a physical UL controlchannel (PUCCH) on the assigned resource blocks in the control section.The UE may transmit only data or both data and control information in aphysical UL shared channel (PUSCH) on the assigned resource blocks inthe data section. A UL transmission may span both slots of a subframeand may hop across frequency.

A set of resource blocks may be used to perform initial system accessand achieve UL synchronization in a physical random access channel(PRACH) 430. The PRACH 430 carries a random sequence and cannot carryany UL data/signaling. Each random access preamble occupies a bandwidthcorresponding to six consecutive resource blocks. The starting frequencyis specified by the network. That is, the transmission of the randomaccess preamble is restricted to certain time and frequency resources.There is no frequency hopping for the PRACH. The PRACH attempt iscarried in a single subframe (1 ms) or in a sequence of few contiguoussubframes and a UE can make only a single PRACH attempt per frame (10ms).

FIG. 5 is a diagram 500 illustrating an example of a radio protocolarchitecture for the user and control planes in LTE. The radio protocolarchitecture for the UE and the eNB is shown with three layers: Layer 1,Layer 2, and Layer 3. Layer 1 (L1 layer) is the lowest layer andimplements various physical layer signal processing functions. The L1layer will be referred to herein as the physical layer 506. Layer 2 (L2layer) 508 is above the physical layer 506 and is responsible for thelink between the UE and eNB over the physical layer 506.

In the user plane, the L2 layer 508 includes a media access control(MAC) sublayer 510, a radio link control (RLC) sublayer 512, and apacket data convergence protocol (PDCP) 514 sublayer, which areterminated at the eNB on the network side. Although not shown, the UEmay have several upper layers above the L2 layer 508 including a networklayer (e.g., IP layer) that is terminated at the PDN gateway 118 on thenetwork side, and an application layer that is terminated at the otherend of the connection (e.g., far end UE, server, etc.).

The PDCP sublayer 514 provides multiplexing between different radiobearers and logical channels. The PDCP sublayer 514 also provides headercompression for upper layer data packets to reduce radio transmissionoverhead, security by ciphering the data packets, and handover supportfor UEs between eNBs. The RLC sublayer 512 provides segmentation andreassembly of upper layer data packets, retransmission of lost datapackets, and reordering of data packets to compensate for out-of-orderreception due to hybrid automatic repeat request (HARQ). The MACsublayer 510 provides multiplexing between logical and transportchannels. The MAC sublayer 510 is also responsible for allocating thevarious radio resources (e.g., resource blocks) in one cell among theUEs. The MAC sublayer 510 is also responsible for HARQ operations.

In the control plane, the radio protocol architecture for the UE and eNBis substantially the same for the physical layer 506 and the L2 layer508 with the exception that there is no header compression function forthe control plane. The control plane also includes a radio resourcecontrol (RRC) sublayer 516 in Layer 3 (L3 layer). The RRC sublayer 516is responsible for obtaining radio resources (i.e., radio bearers) andfor configuring the lower layers using RRC signaling between the eNB andthe UE.

FIG. 6 is a block diagram of an eNB 610 in communication with a UE 650in an access network, in which aspects of the present disclosure may bepracticed. In some cases, the eNB 610 may comprise the eNB 106illustrated in FIG. 1 and/or the eNB 204 illustrated in FIG. 2. Further,in some cases, the UE 650 may comprise the UE 102 illustrated in FIG. 1and/or the UE 206 illustrated in FIG. 2.

For example, eNB 610 and/or UE 650 may determine a maximum modulationorder for the transmission of control channel(s) based on one or moreconditions. Once determined, the eNB 610, for example, may select amodulation and coding scheme (MCS) with a corresponding modulation orderat or below the determined maximum modulation order. The eNB 610 mayselect the MCS for each UE 650 based on channel quality indicators(CQIs) received from the UE 650, process (e.g., encode and modulate) thecontrol data for each UE based on the MCS(s) selected for the UE, andtransmit control information in the control channel(s) using theselected MCS(s).

Similarly, once the UE 650 determines the maximum modulation order forthe eNB 610 to transmit the control channel(s), the UE 650 may monitorfor the control channel(s) transmitted by the eNB 610 at a MCS at orbelow the determined maximum modulation order. The particular MCS usedby the UE 650 may be based on one or more CQI(s) provided to the eNB610.

Referring to the eNB 610, in the DL, upper layer packets from the corenetwork are provided to a controller/processor 675. Thecontroller/processor 675 implements the functionality of the L2 layer.In the DL, the controller/processor 675 provides header compression,ciphering, packet segmentation and reordering, multiplexing betweenlogical and transport channels, and radio resource allocations to the UE650 based on various priority metrics. The controller/processor 675 isalso responsible for HARQ operations, retransmission of lost packets,and signaling to the UE 650. Further, the controller/processor 675 maybe configured to perform one or more of the operations illustrated inFIG. 10, such as generating a first grant that includes information forone or more transmissions on allocated resources in a first subframe andalso generating a second grant that allocates resources in at least asecond subframe to occur after the first subframe.

The TX processor 616 implements various signal processing functions forthe L1 layer (i.e., physical layer). The signal processing functionsincludes coding and interleaving to facilitate forward error correction(FEC) at the UE 650 and mapping to signal constellations based onvarious modulation schemes (e.g., binary phase-shift keying (BPSK),quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK),M-quadrature amplitude modulation (M-QAM)). The coded and modulatedsymbols are then split into parallel streams. Each stream is then mappedto an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot)in the time and/or frequency domain, and then combined together using anInverse Fast Fourier Transform (IFFT) to produce a physical channelcarrying a time domain OFDM symbol stream. The OFDM stream is spatiallyprecoded to produce multiple spatial streams. Channel estimates from achannel estimator 674 may be used to determine the coding and modulationscheme, as well as for spatial processing. The channel estimate may bederived from a reference signal and/or channel condition feedbacktransmitted by the UE 650. Each spatial stream is then provided to adifferent antenna 620 via a separate transmitter 618TX. Each transmitter618TX modulates an RF carrier with a respective spatial stream fortransmission.

In some cases, the transmitter 618TX may be configured to perform one ormore of the operations illustrated in FIG. 10, such as transmitting afirst grant that includes information for one or more transmissions onallocates resources in a first subframe and also transmitting a secondgrant that allocated resources in at least a second subframe to occurafter the first subframe, as explained in greater detail below.

At the UE 650, each receiver 654RX receives a signal through itsrespective antenna 652. Each receiver 654RX recovers informationmodulated onto an RF carrier and provides the information to thereceiver (RX) processor 656. For example, in some cases, the receiver654RX may be configured to perform one or more of the operationsillustrated in FIG. 11, such as receiving a first grant that includesinformation for one or more transmissions on allocates resources in afirst subframe and also receiving a second grant that allocatedresources in at least a second subframe to occur after the firstsubframe, as explained in greater detail below.

The RX processor 656 implements various signal processing functions ofthe L1 layer. The RX processor 656 performs spatial processing on theinformation to recover any spatial streams destined for the UE 650. Ifmultiple spatial streams are destined for the UE 650, they may becombined by the RX processor 656 into a single OFDM symbol stream. TheRX processor 656 then converts the OFDM symbol stream from thetime-domain to the frequency domain using a Fast Fourier Transform(FFT). The frequency domain signal comprises a separate OFDM symbolstream for each subcarrier of the OFDM signal. The symbols on eachsubcarrier, and the reference signal, is recovered and demodulated bydetermining the most likely signal constellation points transmitted bythe eNB 610. These soft decisions may be based on channel estimatescomputed by the channel estimator 658. The soft decisions are thendecoded and deinterleaved to recover the data and control signals thatwere originally transmitted by the eNB 610 on the physical channel. Thedata and control signals are then provided to the controller/processor659.

The controller/processor 659 implements the L2 layer. Thecontroller/processor can be associated with a memory 660 that storesprogram codes and data. The memory 660 may be referred to as acomputer-readable medium. In the UL, the control/processor 659 providesdemultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover upper layer packets from the core network. The upper layerpackets are then provided to a data sink 662, which represents all theprotocol layers above the L2 layer. Various control signals may also beprovided to the data sink 662 for L3 processing. Thecontroller/processor 659 is also responsible for error detection usingan acknowledgement (ACK) and/or negative acknowledgement (NACK) protocolto support HARQ operations. Additionally, in some cases, thecontrol/processor 659 may be configured to act in a determined manneraccording to a first grant and a second grant received. For example, insome cases, the controller/processor 659 may be configured to transmitinformation (e.g., on the UL) based on the received first and secondgrants, as explained below.

In the UL, a data source 667 is used to provide upper layer packets tothe controller/processor 659. The data source 667 represents allprotocol layers above the L2 layer. Similar to the functionalitydescribed in connection with the DL transmission by the eNB 610, thecontroller/processor 659 implements the L2 layer for the user plane andthe control plane by providing header compression, ciphering, packetsegmentation and reordering, and multiplexing between logical andtransport channels based on radio resource allocations by the eNB 610.The controller/processor 659 is also responsible for HARQ operations,retransmission of lost packets, and signaling to the eNB 610.

Channel estimates derived by a channel estimator 658 from a referencesignal or feedback transmitted by the eNB 610 may be used by the TXprocessor 668 to select the appropriate coding and modulation schemes,and to facilitate spatial processing. The spatial streams generated bythe TX processor 668 are provided to different antenna 652 via separatetransmitters 654TX. Each transmitter 654TX modulates an RF carrier witha respective spatial stream for transmission.

The UL transmission is processed at the eNB 610 in a manner similar tothat described in connection with the receiver function at the UE 650.Each receiver 618RX receives a signal through its respective antenna620. Each receiver 618RX recovers information modulated onto an RFcarrier and provides the information to a RX processor 670. The RXprocessor 670 may implement the L1 layer.

The controller/processor 675 implements the L2 layer. Thecontroller/processor 675 can be associated with a memory 676 that storesprogram codes and data. The memory 676 may be referred to as acomputer-readable medium. In the UL, the control/processor 675 providesdemultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover upper layer packets from the UE 650. Upper layer packets fromthe controller/processor 675 may be provided to the core network. Thecontroller/processor 675 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations. Thecontrollers/processors 675, 659 may direct the operations at the eNB 610and the UE 650, respectively.

The controller/processor 675 and/or other processors and modules at theeNB 610 may perform or direct operations, for example, operations 1000in FIG. 10, and/or other processes for the techniques described herein.The controller/processor 659 and/or other processors and modules at theUE 650 may perform or direct operations, for example, operations 1100 inFIG. 11, and/or other processes for the techniques described herein. Incertain aspects, one or more of any of the components shown in FIG. 6may be employed to perform example operations 1000 and 1100 and/or otherprocesses for the techniques described herein. The memories 660 and 676may store data and program codes for the UE 650 and eNB 610respectively, accessible and executable by one or more other componentsof the UE 650 and the eNB 610.

In wireless communication systems (e.g., such as LTE) various modulationschemes, such as BPSK, QPSK, M-PSK, M-QAM, etc., may be supported fordownlink and/or uplink transmissions. LTE (Release-11 and earlier), forexample, may support modulation orders up to 64 QAM. In these systems,BPSK, QPSK and 16 QAM may be supported in uplink and downlinkdirections, whereas 64 QAM may be supported in the downlink direction. Atransmitting wireless device (e.g., BS, UE, etc.) may use a MCS field(e.g., within DCI) to indicate the modulation order to another wirelessdevice. A five bit MCS field may be supported in both DL and ULscheduling grants (e.g., within DCI), and may provide up to twenty-ninedifferent MCSs for efficient rate adaptation.

Based on the MCS index value indicated from the MCS field, the UE maydetermine the number of spatial streams, modulation type, coding rate,and data rate for a given transmission. MCS indices 0-28 may provideexplicit MCS schemes and may be used for both new and re-transmissions.MCS indices 29, 30 and 31 may provide implicit MCS schemes and may beused for re-transmissions.

To enable rate adaptation, and in light of a five bit MCS, the wirelesscommunication system may also support a four bit CQI report. Forexample, the UE may use the four bit CQI report to report sixteenpossible channel conditions experienced by the UE. Based on the reportedCQI, the eNB can schedule up to 29 possible MCS schemes for the UE. Insome cases, the MCS may also be used for transport block size (TBS)lookup. For example, each MCS may be mapped to a TBS lookup index. Inaddition, the MCS index may be further combined with the number ofassigned resource blocks for TBS lookup.

Wireless communication systems (e.g., such as LTE Release 12 (Rel-12)and beyond) may support modulation orders that are higher relative tothose supported in earlier releases of LTE. For example, Rel-12 maysupport up to 256 QAM for downlink transmissions. Such a modulationorder (e.g., 256 QAM) may be used in small cell deployments, e.g., whena UE is likely to experience very good channel conditions.

With the support for 256 QAM, new CQI, MCS, and/or TBS tables may bedefined. For example, new CQI tables may be defined to support CQIfeedback with 256 QAM entries. New MCS tables may be defined to supportscheduling of PDSCH with 256 QAM. New TBS tables may be defined tosupport a larger TBS and therefore a higher peak rate. However, evenwith these new tables defined, the wireless communication system mayassociate a subset of DCI formats with legacy tables while using the newtables for the remaining DCI formats. For example, DCI format 1A/1C maybe associated with the legacy MCS table (i.e., not supporting 256 QAMPDSCH scheduling) while the other DCI formats used for scheduling PDSCHmay use the new MCS tables (i.e., supporting 256 QAM PDSCH scheduling).Further, in some cases, 256 QAM PDSCH scheduling may be supported forC-RNTI based PDSCH transmissions and may not be supported for SPS-RNTIbased PDSCH transmissions. 256 QAM may also be supported for broadcastchannels (e.g., Physical Multicast Channel (PMCH), etc.).

In some cases, UE(s) may be configured to use a combination of differentCQI/MCS tables, e.g., such as a 64 QAM based CQI/MCS table and a 256 QAMbased CQI/MCS table, for decoding/demodulating data channel (e.g.,PDSCH) transmissions. For DL transmission modes 1 to 9, the CQI tablemay be dependent on the set of subframes (within a radio frame period)configured for the UE. For example, if there are two CQI subframe sets,the first set may be associated with a legacy CQI table, and the secondset may be associated with a new CQI table.

In LTE, control channel(s) may be in the form of legacy control channels(e.g., PDCCH), enhanced control channels (e.g., ePDCCH), anmachine-type-communication PDCCH (mPDCCH), etc. In some embodiments,e.g., in LTE Release 14 (Rel-14) certain devices may support low latency(or ultra low latency “ULL”) capability, including the capability toperform certain procedures with low latency relative to devices thatlack the capability (e.g., “legacy” devices). In such cases, controlchannel(s) for low latency operation with shortened TTI (e.g., less than1 ms) may also be used.

As mentioned above, a BS generally notifies UEs of scheduling grants foruplink and downlink transmissions via downlink control information(DCI), which is included in the control channel(s) transmitted to UE(s).For these control channel(s), one or more search spaces may be defined,where each search space includes a set of decoding candidates with oneor more aggregation levels. Each aggregation level generally representsa certain number of resource elements for the control channeltransmission. For legacy PDCCH, for example, an aggregation level L mayinclude L CCEs, where each CCE includes 36 REs. For ePDCCH, eachaggregation level L may include L enhanced CCEs (eCCEs), where each eCCEincludes 36 nominal REs (but some of the REs may not be available for anePDCCH transmission). Thus, with ePDCCH, the number of actual REs for anePDCCH transmission in one eCCE may be less than 36. For controlchannel(s) used with low latency operation, the aggregation level(s) mayhave different CCE sizes. The possible aggregation levels may include 1,2, 4, 8, 16, 32, etc. For each aggregation level, there may be one ormore decoding candidates.

A UE monitors the search spaces (e.g., common search space, UE-specificsearch space, etc.) in order to detect control channel(s) directed tothe UE. In some cases, since the number of CCEs for each of the controlchannel(s) may vary and may not be signaled, a UE may attempt to blindlydecode the control channel(s) in the search spaces. For each aggregationlevel, each UE may try to decode more than one possible candidate. Foreach decoding candidate, there may be one or more DCI sizes. Forexample, there may be one size for DCI format 1A/0, and another size forDCI format 2. For DCI associated with SIMO operation, the DCI size istypically in the range of 30-50 bits. For DCI associated with MIMOoperation, the DCI size is much larger (e.g., 60 to 70 bits, or more).Therefore, the number of blind decodes may be a function of a number ofdecoding candidates and, for each decoding candidate, the possible DCIsize(s).

Example Grant Processing

FIGS. 7A/7B illustrate example downlink (DL) and uplink (UL) subframestructures. For example, FIG. 7A illustrates an example DL centricsubframe structure, which, as shown, comprises control data 702A,downlink data 704A, a gap in transmission (GP) 706A, common uplink data708A, and another gap in transmission 710A. According to certainaspects, a downlink centric subframe may be considered as a subframehaving more downlink symbols than uplink symbols.

FIG. 7B illustrates an example UL centric subframe structure, which, asshown, comprises control data 702B, downlink data 704B, a gap intransmission 706B, uplink data 708B, common uplink data 710B, andanother gap in transmission 712B. According to certain aspects, anuplink centric subframe may be considered as a subframe having moreuplink symbols than downlink symbols. In some cases, for a UL centricsubframe, a UL grant (e.g., as part of the control data 702B) istransmitted at the beginning of the UL centric subframe followed by, forexample as shown in FIG. 7B, uplink data 708B based on the decoded ULgrant.

FIGS. 8A-8C illustrate existing dynamically-switchable subframestructures for dynamic time division duplexing (TDD). For example, FIG.8A illustrates a DL/UL default subframe structure, FIG. 8B illustrates aDL/UL low priority subframe structure, and FIG. 8C illustrates a DL/ULhigh priority subframe structure. As illustrated, the DL/UL defaultsubframe structure shown in FIG. 8A comprises DL/UL scheduling (e.g., bythe BS) 802A, a gap in transmission 804A, DL/UL clear to send (CTS)806A, another gap in transmission 808A, DL/UL data 810A, and UL control(UE) 812A. The DL/UL low priority subframe structure illustrated in FIG.8B comprises DL/UL scheduling (e.g., by the BS) 802B, a gap intransmission 804B, DL/UL data 806B, and UL control (UE) 808B.Additionally, the DL/UL high priority subframe structure illustrated inFIG. 8C comprises DL/UL scheduling (e.g., by the BS) 802C, a gap intransmission 804C, DL/UL override 806C, another gap in transmission808C, DL/UL data 810C, and UL control (UE) 812C.

In some cases, it may be challenging to meet timeline requirements ifthe gap between an UL grant and the corresponding intended transmission(i.e., corresponding to the UL grant) is too small, which may be thecase for the regular UL centric subframe (e.g., as illustrated in FIG.7B). Additionally, for subframe structures used for dynamic TDD, theremay be additional timeline challenges. For example, a user equipment(UE)/evolved node B (eNB) may need to decode the DL/UL grant during theduration of a short gap (e.g., 804A) to decide whether to transmitRTS/CTS (e.g., 806A). Additionally, the UE/eNB may need to decode theRTS/CTS (e.g., 806A) during the duration of a short gap (e.g., 808A) todecide whether to perform/receive a transmission (e.g., 810A). Aspectsof the present disclosure may focus on solutions for enabling samesubframe UL grant in UL centric subframes.

FIGS. 9A-9C illustrate possible solutions to help alleviate the issue oftiming associated with same-subframe UL grants in an UL centricsubframe, which may involve adding extra symbols or gaps between an ULgrant and the corresponding intended transmission. For example, asillustrated in FIG. 9A, one solution may be to add (e.g., to theUL-centric subframe structure illustrated in FIG. 7B) a soundingreference symbol (SRS) before the physical uplink shared channel (PUSCH)(i.e., before the UL data). Another solution, as illustrated in FIG. 9B,may be to add a one-symbol gap between the UL grant and thecorresponding intended UL transmission. Yet another solution, asillustrated in FIG. 9C, may be to use a split grant approach whereresource allocation/rank information is transmitted first and (e.g.,modulation and coding scheme (MCS), new data indicator (NDI), redundancyversion (RV)) is transmitted after.

These solutions, however, may have some drawbacks associated with them.For example, the solution illustrated in FIG. 9A may add additionaloverhead if an SRS is always transmitted before the PUSCH. Likewise, thesolution illustrated in FIG. 9B may add additional overhead due to oneextra symbol being used for the additional gap between the UL grant andcorresponding intended transmission. Similarly, the solution illustratedin FIG. 9C may add additional overhead due to two symbols being used forthe UL grant in the UL centric subframe.

FIG. 10 illustrates example operations 1000 for wireless communications,for example, for helping relieve timing using associated with UL grantprocessing in UL centric subframes, for example, without addingadditional overhead. According to certain aspects, operations 1000 maybe performed by a base station (e.g., one or more of the eNBs 106, 108,204, or 610).

Operations 1000 begin at 1002 by transmitting first subframe thatincludes information for one or more transmissions on allocatedresources in the first subframe. At 1004, the eNB transmits the firstsubframe that with a second grant that allocates resources in at least asecond subframe to occur after the first subframe.

FIG. 11 illustrates example operations 1100 for wireless communications,for example, for helping relieve timing using associated with UL grantprocessing in UL centric subframes. According to certain aspects,operations 1100 may be performed by a user equipment (e.g., one or moreof the UEs 102, 206, or 650).

Operations 1100 begin at 1002 by receiving, in a first subframe, a firstgrant that includes information for one or more transmissions onallocated resources in the first subframe to the user equipment (UE). At1004, the UE receives, in the first subframe, a second grant thatallocates resources in at least a second subframe to occur after thefirst subframe. While not illustrated, operations 1100 may also includeprocessing the first and second grants and performing transmissionsbased on the first and second grants (e.g., one or more ULtransmissions).

The example operations 1000 and 1100 may overcome the drawbacks (e.g.,additional overhead) associated with the solutions illustrated in FIGS.9A-9C, for example, by extending the existing same subframe split grantapproach (e.g., as illustrated in FIG. 9C) to a cross-subframe splitgrant approach. For example, a UL grant may be split into two grants(e.g., Grant A and Grant B). According to certain aspects, configuringthe UL grant in this way alleviates issues with timing associated withsame-subframe UL grants in an UL centric subframe without addingadditional overhead. For example, by configuring the UL grant as twodifferent grants, a UE may have enough time to receive anddecode/process a grant (e.g., Grant A), including information indicatingan allocation of subframes the UE is to perform a UL transmission, andalso have enough time to receive and decode/process a grant (e.g., GrantB), including information indicating how (e.g., a MCS, NDI, RV) toperform the UL transmission, as described in greater detail below.

According to certain aspects, Grant A may be configured to includeinformation needed to generate demodulation reference signals (DMRS)(e.g., rank information and/or a number of resource blocks) while GrantB may be configured to include scheduling information indicating how toperform a UL transmission (e.g., MSC, NDI, RV).

According to certain aspects, Grant A may be transmitted first, and, insome cases, may only be transmitted when information (e.g., informationneeded to generate DMRS) has changed relative to a previous transmissionof Grant A. According to certain aspects, the information in Grant A maytake effect in subframe n+1 or n+k where n is the current subframenumber and k is any number of subframes later. Additionally, accordingto certain aspects, Grant A may also indicate one or more subframes inwhich a UE should perform an uplink transmission.

According to certain aspects and as noted above, Grant B may betransmitted after Grant A. Additionally, Grant B may be transmitted moredynamically than Grant A, similar to a regular UL grant (i.e., an uplinkgrant for a legacy non-UL centric subframe).

According to certain aspects, Grant A may further be configured by theeNB to include information signaling a location that a UE should expectto receive Grant B, which may help reduce the UE's search space (e.g.,as noted above) and reduce the UE's processing latency. Additionally,signaling the location to receive Grant B means that, for a localizedphysical downlink control channel, channel estimation can be relativelylocalized. For example, N resource blocks (RBs) around M RBs may be usedfor PDCCH, where N>M. It should be noted that compared with across-subframe and single grant approach, the eNB has more flexibilityto decide an MCS (e.g., transmitted in Grant B) right before the UE'suplink transmission, which may help improve reliability of the uplinktransmission (e.g., by ensuring the correct MCS for the uplinktransmission based on most recent channel conditions).

FIG. 12 illustrates an example of the cross-subframe split grantapproach described above. For example, as illustrated, Grant A1 may betransmitted by the eNB in a DL centric subframe N (e.g., within controlinformation 1202). According to certain aspects, Grant A1 may indicateto the UE that the UE has three upcoming transmissions (e.g., insubframes N+1, N+2, and N+3). Additionally, as illustrated, Grant B maybe transmitted in subframe N+1 (e.g., within control information 1204)and may comprise MCS information for the UE to use while performing anUL transmission in subframe N+1. Additionally, Grant B may betransmitted in subframe N+2 (e.g., within control information 1206) andmay comprise MCS information for the UE to use while performing the ULtransmission in subframe N+2. Further, Grant A2 may be transmitted inUL-centric subframe N+3 (e.g., within control information 1208) inaddition to Grant B. According to certain aspects, Grant B transmittedin subframe N+3 may still use the resource block (RB) allocationinformation indicated in Grant A1. Additionally, according to certainaspects, Grant A2 may indicate that the UE has one upcoming transmissionin subframe N+4. Further, Grant B may be transmitted in subframe N+4(e.g., within control information 1210) and may comprise MCS informationfor the UE to use while performing the UL transmission in subframe N+4.

According to certain aspects, Grant A and Grant B may be carried indifferent control channels. For example, as illustrated in FIG. 13A,Grant A may be carried in a first control channel (e.g., CC1) whileGrant B may be carried in a second control channel (e.g., CC2).Providing Grant A and Grant B may be advantageous in that it allows forsearch space reduction for Grant B when information regarding thelocation of Grant B is carried in Grant A. According to certain aspects,the search space for Grant A may remain flexible.

Additionally, as illustrated in FIG. 13B, Grant A and Grant B may belogically partitioned within the same control channel (e.g., CC1),reducing channel resources. According to certain aspects, a portion ofthe grant may be applied to a future subframe. For example, Grant A maybe valid from the next upcoming UL centric subframe and Grant B may bevalid for the subframe in which it is received (i.e., a currentsubframe) (e.g., as is the case with Grant A2 and Grant B transmitted insubframe N+3 in FIG. 12).

In some cases, Grant A may be also be applied to the same subframe(i.e., the subframe in which it is received) if there is additional timebetween the UL grant and the corresponding intended uplink transmission,for example, as illustrated in FIG. 14. According to certain aspects,the Grant A may be configured to comprise information indicating that itis to be applied to the subframe in which it is received. Additionally,according to certain aspects, the location of DMRS may be dependent onthe DL portion size of the UL centric subframe. Additionally, in somecases, the search space for Grant A may need to be limited to the firstsymbol of the subframe to avoid timing issues associated with receivingand processing Grant A.

In some cases, Grant A may also be transmitted (i.e., by the eNB) in adata portion of a previous subframe if the previous subframe is a DLcentric subframe. For example, as illustrated in FIG. 15, Grant A may betransmitted in the data portion of the DL centric subframe N and may beapplied to UL subframes N+1 to N+3. Transmitting Grant A within the dataportion of a previous subframe is advantageous as it further reducestiming constraints associated with processing a UL grant in preparationfor a UL transmission.

While aspects of the present disclosure may mean that some flexibilityin the ability to change resources may be sacrificed and may increaseerror events and overhead on control resources, the solutions presentedherein may be advantageous in that they allow same-subframe schedulingof PUSCH and overhead reduction of DL symbols in UL centric subframe.

It should be noted that while aspects of the present disclosure arelargely directed to UL centric subframes and UL grants, the techniquespresented herein may also be applied to the DL where split grants aretransmitted in different subframes.

Additionally, it should be noted that while aspects of the presentdisclosure are generally directed to operations performed by a basestation, aspects of the present disclosure may also be directed tocorresponding operations performed, for example, by a user equipment.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover a, b, c,a-b, a-c, b-c, and a-b-c, as well as any combination with multiples ofthe same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b,b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

In some cases, rather than actually transmitting a frame, a device mayhave an interface to output a frame for transmission. For example, aprocessor may output a frame, via a bus interface, to an RF front endfor transmission. Similarly, rather than actually receiving a frame, adevice may have an interface to obtain a frame received from anotherdevice. For example, a processor may obtain (or receive) a frame, via abus interface, from an RF front end for transmission.

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in figures, those operations mayhave corresponding counterpart means-plus-function components withsimilar numbering.

For example, means for transmitting may comprise a transmitter, such astransmitter 618 of the eNB 610 or transmitter 654 of the UE 650, and/orone or more antennas, such as the antenna 620 of the eNB 610 or theantenna 652 of the UE 650. Means for receiving may comprise a receiver,such as receiver 618 of the eNB 610 or receiver 654 of the UE 650,and/or one or more antennas, such as the antenna 620 of the eNB 610 orthe antenna 652 of the UE 650. Additionally, means for configuring maycomprise a processing system, including one or more processors, such asthe TX Processor 616, the RX processor 670, or the Controller/Processor675 of the eNB 610 and/or the TX Processor 668, the RX processor 656, orthe Controller/Processor 659 of the UE 650, illustrated in FIG. 6.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device (PLD),discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

If implemented in hardware, an example hardware configuration maycomprise a processing system in a wireless node. The processing systemmay be implemented with a bus architecture. The bus may include anynumber of interconnecting buses and bridges depending on the specificapplication of the processing system and the overall design constraints.The bus may link together various circuits including a processor,machine-readable media, and a bus interface. The bus interface may beused to connect a network adapter, among other things, to the processingsystem via the bus. The network adapter may be used to implement thesignal processing functions of the PHY layer. In the case of a userterminal 120 (see FIG. 1), a user interface (e.g., keypad, display,mouse, joystick, etc.) may also be connected to the bus. The bus mayalso link various other circuits such as timing sources, peripherals,voltage regulators, power management circuits, and the like, which arewell known in the art, and therefore, will not be described any further.The processor may be implemented with one or more general-purpose and/orspecial-purpose processors. Examples include microprocessors,microcontrollers, DSP processors, and other circuitry that can executesoftware. Those skilled in the art will recognize how best to implementthe described functionality for the processing system depending on theparticular application and the overall design constraints imposed on theoverall system.

If implemented in software, the functions may be stored or transmittedover as one or more instructions or code on a computer-readable medium.Software shall be construed broadly to mean instructions, data, or anycombination thereof, whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.Computer-readable media include both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. The processor may beresponsible for managing the bus and general processing, including theexecution of software modules stored on the machine-readable storagemedia. A computer-readable storage medium may be coupled to a processorsuch that the processor can read information from, and write informationto, the storage medium. In the alternative, the storage medium may beintegral to the processor. By way of example, the machine-readable mediamay include a transmission line, a carrier wave modulated by data,and/or a computer readable storage medium with instructions storedthereon separate from the wireless node, all of which may be accessed bythe processor through the bus interface. Alternatively, or in addition,the machine-readable media, or any portion thereof, may be integratedinto the processor, such as the case may be with cache and/or generalregister files. Examples of machine-readable storage media may include,by way of example, RAM (Random Access Memory), flash memory, ROM (ReadOnly Memory), PROM (Programmable Read-Only Memory), EPROM (ErasableProgrammable Read-Only Memory), EEPROM (Electrically ErasableProgrammable Read-Only Memory), registers, magnetic disks, opticaldisks, hard drives, or any other suitable storage medium, or anycombination thereof. The machine-readable media may be embodied in acomputer-program product.

A software module may comprise a single instruction, or manyinstructions, and may be distributed over several different codesegments, among different programs, and across multiple storage media.The computer-readable media may comprise a number of software modules.The software modules include instructions that, when executed by anapparatus such as a processor, cause the processing system to performvarious functions. The software modules may include a transmissionmodule and a receiving module. Each software module may reside in asingle storage device or be distributed across multiple storage devices.By way of example, a software module may be loaded into RAM from a harddrive when a triggering event occurs. During execution of the softwaremodule, the processor may load some of the instructions into cache toincrease access speed. One or more cache lines may then be loaded into ageneral register file for execution by the processor. When referring tothe functionality of a software module below, it will be understood thatsuch functionality is implemented by the processor when executinginstructions from that software module.

Also, any connection is properly termed a computer-readable medium. Forexample, if the software is transmitted from a website, server, or otherremote source using a coaxial cable, fiber optic cable, twisted pair,digital subscriber line (DSL), or wireless technologies such as infrared(IR), radio, and microwave, then the coaxial cable, fiber optic cable,twisted pair, DSL, or wireless technologies such as infrared, radio, andmicrowave are included in the definition of medium. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Thus, in some aspects computer-readable media maycomprise non-transitory computer-readable media (e.g., tangible media).In addition, for other aspects computer-readable media may comprisetransitory computer-readable media (e.g., a signal). Combinations of theabove should also be included within the scope of computer-readablemedia.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

What is claimed is:
 1. A method of wireless communication, comprising:transmitting a first subframe comprising a first grant that includesinformation for one or more transmissions on allocated resources in thefirst subframe, wherein the first subframe comprises more uplink symbolsthan downlink symbols; and transmitting the first subframe with a secondgrant that allocates resources in at least a second subframe to occurafter the first subframe, wherein: the second grant comprisesinformation indicating an expected location to receive the first grantin at least one of the first subframe or a subsequent subframe; thesecond grant comprises information for generating a demodulationreference signal (DMRS) in the second subframe; and the information forgenerating the DMRS comprises at least a number of resource blocks forthe DMRS.
 2. The method of claim 1, wherein: the information forgenerating the DMRS further comprises rank information.
 3. The method ofclaim 1, further comprising at least one of: configuring the secondgrant to comprise information indicating at least one subframe in whichto perform an uplink transmission; or transmitting the second grant onlywhen information in the second grant has changed relative to a previoustransmission of the second grant.
 4. The method of claim 1, wherein thefirst grant comprises information indicating a modulation and codingscheme.
 5. The method of claim 1, wherein the first grant and the secondgrant are transmitted in different control channels.
 6. The method ofclaim 1, wherein: the second grant also allocates resources in the firstsubframe; and a search space of the second grant is limited to a firstsymbol of the first subframe.
 7. The method of claim 1, furthercomprising: configuring a third grant to comprise information forgenerating a reference signal in the second subframe; and transmittingthe third grant within a data portion of a downlink subframe having moredownlink symbols than uplink symbols.
 8. A method of wirelesscommunication by a user equipment (UE), comprising: receiving, in afirst subframe comprising more uplink symbols than downlink symbols, afirst grant that includes information for one or more transmissions onallocated resources in the first subframe; and receiving, in the firstsubframe a second grant that allocates resources in at least a secondsubframe to occur after the first subframe, wherein: the second grantcomprises information indicating an expected location to receive thefirst grant in at least one of the first subframe or a subsequentsubframe; the second grant comprises information for generating ademodulation reference signal (DMRS) in the second subframe; and theinformation for generating the DMRS comprises at least a number ofresource blocks for the DMRS.
 9. The method of claim 8, wherein: theinformation for generating the DMRS further comprises rank information.10. The method of claim 8, wherein at least one of: the second grantcomprises information indicating at least one subframe in which toperform an uplink transmission; or the second grant is received onlywhen information in the second grant has changed relative to a previoustransmission of the second grant.
 11. The method of claim 8, wherein thefirst grant comprises information indicating a modulation and codingscheme.
 12. The method of claim 8, wherein the first grant and thesecond grant are received in different control channels.
 13. The methodof claim 8, wherein: the second grant also allocates resources in thefirst subframe; and a search space of the second grant is limited to afirst symbol of the first subframe.
 14. The method of claim 8, furthercomprising receiving a third grant within a data portion of a downlinksubframe having more downlink symbols than uplink symbols, wherein thethird grant comprises information for generating a reference signal inthe second subframe.
 15. An apparatus for wireless communication,comprising: at least one processor configured to: generate a first grantthat includes information for one or more transmissions on allocatedresources in a first subframe comprising more uplink symbols thandownlink symbols; generate a second grant that allocates resources in atleast a second subframe to occur after the first subframe, wherein: thesecond grant comprises information indicating an expected location toreceive the first grant in at least one of the first subframe or asubsequent subframe; the second grant comprises information forgenerating a demodulation reference signal (DMRS) in the secondsubframe; and the information for generating the DMRS comprises at leasta number of resource blocks for the DMRS; and a transmitter configuredto transmit the first grant and the second grant in the first subframe.16. The apparatus of claim 15, wherein: the information for generatingthe DMRS further comprises rank information.
 17. The apparatus of claim15, wherein at least one of: the second grant comprises informationindicating at least one subframe in which to perform an uplinktransmission; or the transmitter is further configured to transmit thesecond grant only when information in the second grant has changedrelative to a previous transmission of the second grant.
 18. Theapparatus of claim 15, wherein the first grant comprises informationindicating a modulation and coding scheme.
 19. The apparatus of claim15, wherein the first grant and the second grant are transmitted indifferent control channels.
 20. The apparatus of claim 15, wherein: thesecond grant also allocates resources in the first subframe; and asearch space of the second grant is limited to a first symbol of thefirst subframe.
 21. An apparatus for wireless communications,comprising: a receiver configured to: receive, in a first subframecomprising more uplink symbols than downlink symbols, a first grant thatincludes information for one or more transmissions on allocatedresources in the first subframe; and receive, in the first subframe asecond grant that allocates resources in at least a second subframe tooccur after the first subframe, wherein: the second grant comprisesinformation indicating an expected location to receive the first grantin at least one of the first subframe or a subsequent subframe; thesecond grant comprises information for generating a demodulationreference signal (DMRS) in the second subframe; and the information forgenerating the DMRS comprises at least a number of resource blocks forthe DMRS.
 22. The apparatus of claim 21, wherein: the information forgenerating the DMRS further comprises rank information.
 23. Theapparatus of claim 21, wherein at least one of: the second grantcomprises information indicating at least one subframe in which toperform an uplink transmission; or the second grant is only receivedwhen the information in the second grant has changed relative to aprevious transmission of the second grant.
 24. The apparatus of claim21, wherein the first grant comprises information indicating amodulation and coding scheme.
 25. The apparatus of claim 21, wherein thefirst grant and the second grant are received in different controlchannels.
 26. The apparatus of claim 21, wherein: the second grant alsoallocates resources in the first subframe; and a search space of thesecond grant is limited to a first symbol of the first subframe.
 27. Theapparatus of claim 21, wherein the receiver is further configured toreceive a third grant within a data portion of a downlink subframehaving more downlink symbols than uplink symbols, wherein the thirdgrant comprises information for generating a reference signal in thesecond subframe.